1. Field of the Invention
The present invention relates generally to furcation tubing for transitioning a multi-fiber optical cable into individual optical fibers, and to a fanout furcation kit for separating the optical fibers of a multi-fiber optical cable into individual optical fibers and protecting the optical fibers at the separation location.
2. Description of the Related Art
Furcation tubing is used throughout fiber optic networks to transition multi-fiber optical cables into individual optical fibers. The individual optical fibers are typically separated from the multi-fiber optical cable using a fanout furcation kit and terminated to a fiber optic connector or optical device, such as optical switching or cross-connecting equipment. The two most common materials currently being used in fiber optic networks for furcation tubing are polyvinylidene fluoride (PVDF) and clear, etched polytetrafluoroethylene (PTFE), commonly known as Teflon. Although each of these materials provides certain advantages, both have one or more undesirable characteristics when used in conjunction with fanout furcation kits and fiber optic connectors or optical devices.
PVDF is readily available in the twelve standard colors utilized in the telecommunications industry for fiber identification and provides acceptable tensile bond strength when secured to a fanout furcation kit, fiber optic connector or optical device using a conventional epoxy adhesive. PVDF furcation tubing, however, experiences excessive longitudinal shrinkage when exposed to the extreme temperatures and/or temperature cycling encountered in some outdoor installations. Excessive shrinkage can cause unacceptable attenuation (i.e., transmission loss) due to micro-bending of the optical fibers within the furcation tubing and movement of the optical fibers within the fanout furcation kit, fiber optic connector or optical device. As a result, PVDF furcation tubing must be pre-conditioned during manufacture to minimize the amount of longitudinal shrinkage that occurs with exposure to extreme temperatures and temperature cycling. In some instances, however, factory pre-conditioning has been insufficient to prevent unacceptable attenuation and micro-damage to optical fibers in fanout furcation kits deployed in some outdoor installations.
Clear, etched PTFE furcation tubing provides a more favorable coefficient of thermal expansion (CTE), and therefore, considerable less longitudinal shrinkage in extreme temperatures and/or temperature cycling. PTFE furcation tubing, however, has certain other undesirable characteristics for use with fanout furcation kits and fiber optic connectors or optical devices. Even though the PTFE tubing can be chemically etched to enhance bonding, greater tensile bond strength is oftentimes required when used in fanout furcation kits and for termination to fiber optic connectors or optical devices. In addition, PTFE furcation tubing is not readily available in the twelve standard colors utilized in the telecommunications industry for fiber identification. Regardless, PTFE furcation tubing that is available in different colors typically changes color when chemically etched to increase tensile bond strength.
Regardless of the type of furcation tubing used, a slight amount of movement of an optical fiber within a conventional fanout furcation kit is inevitable. In an effort to prevent further ingress of an optical fiber into a fanout furcation kit as a result of longitudinal shrinkage of the furcation tubing, the funnel area of the furcation body may be filled with an epoxy or acrylate to limit movement of the optical fibers during extreme temperatures and temperature cycling. However, existing fanout furcation kits filled with an epoxy or acrylate continue to experience unacceptable attenuation and micro-damage to optical fibers installed in an outdoor fiber optic network. In some instances, the epoxy or acrylate drains out of the funnel area during the cure cycle, resulting in insufficient adhesion to the optical fibers, or exposure of the optical fibers to the ambient environment. More viscous epoxies and acrylates have been used to reduce drainage with only limited success since a more viscous epoxy or acrylate increases the likelihood of developing voids that reduce adhesion and expose the optical fibers to the ambient environment. In other instances, the optical fibers are not fully encapsulated by the epoxy or acrylate since some of the optical fibers are positioned immediately below another optical fiber, and thus, are not readily visible during assembly, while the funnel area is being filled with the epoxy or acrylate, and after the epoxy or acrylate is cured.
Based on the foregoing, it is apparent improved furcation tubing is needed that provides reduced longitudinal shrinkage and increased tensile bond strength in the twelve standard colors utilized in the telecommunications industry for fiber identification. An improved fanout furcation kit is also needed that prevents movement of the optical fibers in the funnel area of the furcation body as a result of exposure to extreme temperatures and temperature cycling. Use of the improved furcation tubing and fanout furcation kit significantly reduces the likelihood of unacceptable attenuation and micro-damage to optical fibers deployed in an outdoor fiber optic network.